Kirsten's investigation began after she saw photographers complaining about copyright violations on Facebook. She wondered why Facebook could get in trouble for copyright violation and Pinterest couldn't.

She browsed Pinterest's Terms of Use section. In it she found Pinterest's members are solely responsible for what they pin and repin. They must have explicit permission from the owner to post everything.

"I immediately thought of the ridiculously gorgeous images I had recently pinned from an outside website, and, while I gave the other photographer credit, I most certainly could not think of any way that I either owned those photos or had a license, consent or release from the photographer who owned them," Kirsten writes.

Pinterest encourages repinning community photos though, so Kirsten found it hard to believe the act was unlawful. She continued to dig.

Kirsten turned to federal copyright laws and found a section on fair use. Copyrighted work can only be used without permission when someone is criticizing it, commenting on it, reporting on it, teaching about it, or conducting research. Repinning doesn't fall under any of those categories.

The one glimmer of hope for Pinterest, Kirsten writes, is the outcome of Kelly v. Arriba Soft Corporation. In that case, a photographer sued a search engine. The search engine won because it used thumbnail images in its results, not the entire work.

Thumbnails aren't always fair use, however. They're only fair use if the necessary portion of the work is copied and nothing more. Pinterest, however, lifts the entire image from the original source which is not ok.

If that didn't scare Kirsten enough, the all caps section of Pinterest's Terms of Use did.

Pinterest writes:

“YOU ACKNOWLEDGE AND AGREE THAT, TO THE MAXIMUM EXTENT PERMITTED BY LAW, THE ENTIRE RISK ARISING OUT OF YOUR ACCESS TO AND USE OF THE SITE, APPLICATION, SERVICES AND SITE CONTENT REMAINS WITH YOU.”

What's more, Pinterest places all blame and potential legal fees on its users. It writes:

"You agree to defend, indemnify, and hold Cold Brew Labs, its officers, directors, employees and agents, harmless from and against any claims, liabilities, damages, losses, and expenses, including, without limitation, reasonable legal and accounting fees, arising out of or in any way connected with (i) your access to or use of the Site, Application, Services or Site Content, (ii) your Member Content, or (iii) your violation of these Terms.”

Basically, if a photographer sues you for pinning an image illegally on Pinterest, the user must not only pay for his or her lawyer, they must also pay for Pinterest's lawyer. In addition, the defendant must pay all charges against him or herself, along with all of Pinterest's charges.

Kirsten likens Pinterest to Napster as an enabler of illegal activity. It wasn't just Napster that went down -- 12 year old girls who downloaded music were sued too.

She concludes:

"My initial response is probably the same as most of yours: 'Why [can't I pin their work]? I’m giving them credit and it’s only creating more exposure for them and I LOVE when people pin my stuff!' But then I realized, I was unilaterally making the decision FOR that other photographer...Bottom line is that it is not my decision to make. Not legally and not ethically."